This protocol is a pilot study on standard care. The main goal is to assess the impact of positioning on lumbar puncture process especially on pain sensitivity in children.

It's a prospective, monocentric, randomized, open-label, cross-over study. Inclusion period is one year, and number of inclusions forecasted is about 30. Each patient will have one LP in a seated position and one in a lying position.

In Pediatric Oncology Hematology, invasive procedures such lumbar punctures or myelograms are essential to diseases diagnosis and treatment.

In hematological malignancies, lumbar punctures are particularly frequent as the therapy processes. Despite a good analgesia, this repeated procedure can generate pain, anxiety, apprehension leading to an increasing difficulty in the procedure realization.

Two positions are possible to carry out lumbar puncture: seated or lying position.

The main goal of this study is to assess the impact of the child positioning during the lumbar puncture process in term of pain, anxiety and stress.

This study is a prospective, monocentric, randomized, open-label, cross-over study. Inclusion period is 1 year, 30 patients will be included from 2 to 18 years old.

Each patient will have 2 LP one in seated and one in lying position in a specific order determined by randomization.

All data regarding pain and anxiety will be collected the day of LP. Patients will be re contacted 48 hours and 15 days after LP procedure in order to evaluate complications such post-lumbar puncture syndrome or hematoma. The main analysis will be done on intent-to-treat-analysis basis and will compare pain intensity between the two groups.

Inclusion Criteria:

• Age between 2 and 18 years old
• Patients requiring at least 2 therapeutic lumbar punctures
• Patients able to receive analgesic procedure according to 20005 good practices recommendation
• Presence of one parent during LP procedure
• Child able to use assessment scales
• LP realized with a 20 G needle
• Platelets > 50000
• Child with prior clinical examination
• Affiliated to a health care insurance regimen

Exclusion Criteria:

• Seated or lying position impossible
• Lumbar puncture contraindication
• Patient or parent opposition to second LP realization in the required position
• Clotting trouble on LP day not allowing the LP procedure